Electrified vehicles reduce both fuel consumption and exhaust emissions by employing electric drive systems energized by a high voltage (HV) energy storage device (ESD) such as an HV battery. Battery electric vehicles (BEVs) and Plug-in electric vehicles (PEVs) may be designed to rely totally on electric motoring power, while hybrid electric vehicles (HEVs) and plug-in HEVs (PHEVs) may use an electric drive system in conjunction with an internal combustion engine. Unlike a traditional vehicle, in which a low voltage battery provides the energy required to start an engine, an HEV relies on a HV battery or other type of HV ESD to start a vehicle in place of a conventional starter motor to crank the engine. While plug-in vehicles are configured to plug into a wall socket or power grid to recharge a HV battery pack using AC power, standard HEVs are generally not designed with that capability. Rather, an HEV battery is typically charged by the vehicle engine and regenerative braking while the vehicle is being operated. Therefore, when an HEV can't be started, charging its depleted battery can pose a challenge.
In addition to its environmentally friendly features, an HEV can also have several consumer-friendly features. For example, an HEV can have a keyless start feature in which an operator can start the vehicle by either pushing a start button at the dashboard, or by bringing a key fob in proximity of a detector that can start the vehicle as a response to fob detection. While these features can be convenient, they can also unfortunately, facilitate operator carelessness. For example, such features can make it easy for a driver to inadvertently exit and leave an electric vehicle while it is still running. In a traditional automobile, even those that are relatively quiet, the engine can generally be heard inside and outside the vehicle when it is running. Consequently, the likelihood of a driver unwittingly leaving a vehicle when the engine is still operating is relatively low. Furthermore, removal of an ignition key generally requires the engine to be turned off prior to key removal. However, in an HEV in which the electric drive system is running but the engine is not, there is no noise to remind an operator of a parked vehicle that the vehicle drive system is still on and consuming power. In a vehicle in which there is no key to remove after parking, it can be even easier for a driver to forget to turn off the vehicle. Leaving a vehicle on for relatively short periods, for example while grocery shopping or during a shopping expedition at the mall, may not pose a serious problem unless already at a low battery state of charge. However, leaving it parked and turned on for an extended period can discharge the high voltage battery to a point that it can no longer start the vehicle. For example, in his hurry to catch a flight at an airport, a driver may park his vehicle, quickly unload his baggage, and scramble to the terminal. In his haste, he could completely forget to power off his HEV. Upon his return 4-5 days later he may be unable to crank the engine because the HV battery voltage is below the minimum required to start the vehicle. Unlike the owner of a BEV or PHEV who can plug his vehicle to a public charging grid at the airport to recharge a battery, an HEV owner will have to seek outside help. Much to his chagrin, particularly if it is late at night, he will have to contact a roadside assistance service that can dispatch a service vehicle equipped to charge the depleted battery or tow to a vehicle dealership. A similar situation can arise under other circumstances, such as when the vehicle is inadvertently left on at home, when there is a battery malfunction, or while the vehicle is being repaired at a service facility. Battery charging equipment can often include a voltage converter adapted to charge a battery. A mechanical interlock may be used to connect the equipment with the depleted HV battery. One of the primary drawbacks of current recharging methods is that the HV battery is charged while it is connected to one or more vehicle components or systems, i.e., the HV battery is “on-line” in order to receive the necessary control messages required to allow and enable battery charging.